what are node set fragments and why are they ruining my life?

["Mark D. Anderson" <mda@xxxxxxxxxxxxxx>]

see the minimal xsl and xml file below.

first off, nothing i've read in the spec or the various xsl tutorials
make any sense in defining what a node set fragment is.
they talk about things like "not being well-formed", but (a) i'm not
clear how one is able to produce something that isn't well-formed,
and (b) that doesn't match experience as this example shows.

here i've shown where the mere act of passing a node set (fragment)
through a call-template is enough to defile it.

here are the various outputs.

1. comment out first for-each, use xt
output is:
member 1

note that there is a result, but no xsl:message instructions are run

2. comment out first for-each, use saxon
output is:
member local-name=member, id=1
member local-name=member, id=2

note that there is no result, but the xsl:message instructions are run

3. leave in first for-each, use xt
output is:
cannot convert to node-set

4. leave in first for-each, use saxon
member local-name=member, id=1
member local-name=member, id=2
Error during source document processing
At xsl:for-each on line 32 of file:/d:/mda/projects/xmlhacks/xmlidl/test1.xsl: Cannot convert value [** RESULT TREE FRAGMENT **] to
a node-set

Thanks to anyone who can elucide this matter.

-mda

test1.xml

<root>
  <member id="1">member 1</member>
  <member id="2">member 2</member>
</root>


test1.xsl

<?xml version="1.0" ?>

<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
  xmlns:date="http://www.jclark.com/xt/java/java.util.Date";
  xmlns:xt="http://www.jclark.com/xt";
  xmlns:sxf="/com.icl.saxon.functions.Extensions"
  extension-element-prefixes="date xt sxf"
  exclude-result-prefixes="date sxf xt"
  >
  <xsl:output
     method="html"
     indent="yes"
     doctype-public="-//W3C//DTD HTML 4.0 Transitional//EN"
  />
  <xsl:strip-space elements="*"/>

  <xsl:template match="root">
    <xsl:variable name="members">
      <xsl:call-template name="get_members"/>
    </xsl:variable>
    <!-- why can't i use a variable? something about result tree fragments... -->

    <!-- comment this for-each out to avoid the runtime error
    <xsl:for-each select="$members">
      <xsl:message>member local-name=<xsl:value-of select="local-name(.)"/>, id=<xsl:value-of select="@id"/></xsl:message>
    </xsl:for-each>
    -->
    <xsl:value-of select="$members"/>
  </xsl:template>

  <xsl:template name="get_members">
    <xsl:variable name="result" select="*"/>
    <xsl:for-each select="$result">
      <xsl:message>member local-name=<xsl:value-of select="local-name(.)"/>, id=<xsl:value-of select="@id"/></xsl:message>
    </xsl:for-each>
    <!-- same thing as: <xsl:value-of select="$result"/> -->
    <xsl:value-of select="*"/>
  </xsl:template>

</xsl:stylesheet>



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